In the United States, a District Attorney (DA) represents the state government in the prosecution of criminal offenses, and is the chief law enforcement officer and legal officer of that state's jurisdiction.
The prosecution is the legal party responsible for presenting the case against an individual who is suspected of breaking the law, initiating and directing further criminal investigations, guiding and recommending the sentencing of offenders, and are the only attorneys allowed to participate in grand jury proceedings.
The district attorney supervises a staff of prosecutors, Assistant District Attorneys (ADAs), who represent the State and prosecute criminals on behalf of the District Attorney. Depending upon the system in place, DAs may be appointed by the chief executive of the jurisdiction or elected by the voters of the jurisdiction.
The United States Judiciary Act of 1789, Section 35, provided for the appointment of a person in each judicial district to prosecute federal crimes and to represent the United States in all civil actions to which it was a party. Initially, there were 13 districts to cover the 11 States that had by that time ratified the constitution. Each State was a district, except for Massachusetts and Virginia which formed two. Districts were added when additional States were admitted. The statute did not confer a title upon these local agents of federal authority, but subsequent statutes and court decisions referred to them most frequently as "district attorneys". In 1948, the Judicial Code adopted the term "United States attorneys".
This term for a prosecutor originates with the traditional use of the term "district" for multi-county prosecutorial jurisdictions in several U.S. states. For example, New York appointed prosecutors to multi-county districts prior to 1813. Even after those states broke up such districts and started appointing or electing prosecutors for individual counties, they continued to use the title "district attorney" for the most senior prosecutor in a county rather than switch to "county attorney".
At the local level in other jurisdictions, officers such as the commonwealth's attorney, state's attorney, county attorney, circuit solicitor, or county prosecutor carry out functions similar to those performed by a district attorney.
The title of "District Attorney" and "Assistant District Attorney", is the most commonly given official name to state prosecutors, and is used by several major jurisdictions within the United States, such as New York, California, Texas, Pennsylvania, Delaware, Massachusetts, North Carolina, Georgia, Nevada, Wisconsin, Oregon, and Oklahoma. In St. Louis, Missouri, the title is circuit attorney.
In the United Kingdom, the equivalent position to the District Attorney is the Chief Crown Prosecutor, and the equivalent to an Assistant District Attorney is a Crown Prosecutor. These prosecutors work under the Crown Prosecution Service in England and Wales, the Procurator Fiscal in Scotland, and the Director of Public Prosecutions in Northern Ireland. In many other countries, the title of the chief prosecuting officer is Director of Public Prosecutions.
In Canada, the equivalent position to the District Attorney is the Crown Attorney, Crown Counsel or Crown Prosecutor depending on the province, and the equivalent to an Assistant District Attorney is the Assistant Crown Attorney, Assistant Crown Counsel or Assistant Crown Prosecutor respectively. Except in Ontario, the chief prosecutor is an appointed position.
The Assistant District Attorney (ADA), or state prosecutor, is a public official who represents the state government on behalf of the District Attorney (DA) in the prosecution of alleged criminals. In carrying out their duties, ADAs have the authority to investigate persons, issue subpoenas, file formal criminal charges, plea bargain with defendants, and grant immunity to witnesses and accused criminals.
An administrative assistant district attorney (Admin ADA), executive assistant district attorney (Exec ADA), chief assistant district attorney (Chief ADA), or first assistant district attorney (First ADA) respectively, are some of the titles given to the leadership of senior ADAs working under the DA. The First ADA is generally considered the second-in-command for the office, and usually report directly to the DA. The exact roles and job assignments for each title vary with each individual office, but generally include management of the daily activities and supervision of specialized divisions within the office. Often, a senior ADA may oversee or prosecute some of the larger crimes within the jurisdiction. In some offices, the Exec ADA has the responsibility of hiring lawyers and support staff, as well as supervising press-releases and overseeing the work of the office.